1. Field of the Invention
The present invention relates generally to dental implants and, more particularly, methods and devices for installing a dental implant.
2. Description of the Related Art
Restoration of an edentulous area of the mouth serves multiple functions, including improved aesthetics, improved mastication, maintenance of crestal bone, and providing for an occlusal stop for a reproducible bite. Restoration can be accomplished using a standard bridge, a removable appliance (a partial or full denture), or a dental implant.
Dental implantation is a procedure for replacing a missing tooth using a dental implant. The placement of the implant is usually accomplished in four stages. In a first stage, a dentist reviews radiographs and dental models to determine the proper placement and axial alignment of the implant. In a second stage, a dental surgeon accesses the bone through the mucosal tissue. With the use of a prefabricated stint, the surgeon drills or bores out the maxillary or mandibular bone. The implant is then either pressed or screwed into the bone. A healing cap is typically then placed over the implant and the surrounding mucosal tissues are sutured over the healing cap. This provides for a biologically closed system to allow osteointegration of bone with the implant. Complete osteointegration typically takes anywhere from four to ten months.
Stage three, involves a second surgical procedure during which the dental surgeon makes an incision in the mucosal tissue to expose the osteointegrated implant. The healing cap is removed and a temporary abutment, having a height at least equal to the thickness of the gingival tissue or a final prosthetic abutment, is coupled to the implant. Once the abutment is secured an immediate mold or impression may be taken. In a modified procedure, the impression may be taken within one to two weeks after stage three. The impression is used to record the axial position and orientation of the implant, which is then reproduced in a stone or plaster analogue of the patient's mouth. The main objective of the impression is to properly transfer the size and shape of adjacent teeth in relation to the permanently placed implant and the precise configuration and orientation of the abutment to the dental technician. The plaster analogue provides the laboratory technician with a precise model of the patient's mouth, including the orientation of the implant fixture relative to the surrounding teeth. Based on this model, the technician constructs a final restoration. Stage four, in the restorative process, involves replacing the temporary healing abutment with the final restoration.
As noted above, during stage three, a mold or impression is taken of the patient's mouth to accurately record the position and orientation of the implant site and to provide the information needed to fabricate the restorative replacement and/or intermediate prosthetic components. There are several conventional methods for taking this impression.
One method involves a conventional transfer coping. Transfer copings have an impression portion adapted to form a unique or indexed impression in the impression material and a base portion having mating indexing means adapted to mate with the exposed indexing means of the implant or prosthetic abutment. In use, the transfer coping is temporarily secured to the exposed proximal end of the implant fixture such that the mating indexing means of the impression coping and implant are interlockingly mated to one another. Typically, a threaded screw or bolt is used to temporarily secure the transfer coping to the implant fixture.
Once the impression coping is secured to the implant fixture, an impression of the transfer coping relative to the surrounding teeth is taken. Typically, this involves a “U” shaped tray filled with an impression material that is placed in the patient's mouth over the implant site. The patient bites down on the tray, squeezing the impression material into the implant site and around the transfer coping. Within a few minutes, the impression material cures or hardens to a flexible, resilient consistency. The impression tray is then removed from the patient's mouth to reveal an impression of the implant site and the transfer coping. The restorative dentist then removes the transfer coping from the patient's mouth and transfers the transfer coping back into the impression material, being careful to preserve the proper orientation of the indexing means.
Another method typically involves a conventional pick-up coping. Pick-up copings are similar to the transfer copings described above; except that a pick-up coping typically includes an embedment portion adapted to be non-removably embedded within the impression material. Typically, the embedded portion comprises a protuberant “lip” or similar embedment projection at a coronal portion of the coping. This allows for “grabbing” or traction of the impression material as the tray is being removed from the patient's mouth. The pick-up copings are “picked up” and remain in the impression material when the tray is removed from the patient's mouth.
Yet another method for taking an impression involves an impression or transfer cap. Impression or transfer caps are placed over or on the built-up part of the abutment or the implant and remain in the impression material when the tray is removed. There are several different types of transfer caps. One type of transfer cap has a tapered inner surface, which is adapted in form and size to the built-up part or abutment of the implant. This cap has an inner surface, which has indentations or slots, which correspond to indentation or slots present on the abutment. The cap is attached to the abutment with resilient flaps or tongues. An example of such a cap is illustrated in U.S. Pat. No. 5,688,123 to Meiers et al.